Fotasy FHL 42mm Focusing Helicoid Adapter 35mm - 90mm, Black This focusing Helicoid tube is made with light-weight alloy t is useful for those lenses without focus ring. It could be used as Macro barrel, and offers fine focus control for macro photography The length of this Helicoid tube 35mm to 90mm (max), it offers a total of 55mm movement distance for lens focusing. User can use it with M42 screw mount lenses, such as Carl Zeiss, and even enlarger lenses. Very useful for enlarge lens, some of them are Leica 39mm / M39 / L39 mount. You may need an additional 39mm-42mm adapter.